The present invention relates to a master cylinder for a vehicle hydraulic brake or clutch system and particularly to the retention of the piston thereof.
An hydraulically actuated clutch or brake system of a motor vehicle requires that the master cylinder, which is actuated by the brake pedal, also take up rearwardly directed forces which occur, for instance, when the driver rapidly releases the pedal and the pedal, acted on by the return spring, returns rapidly into its starting position or when, by mistake, the foot of the driver is below the pedal and "pulls" up on it. These forces can become very large as a result of the leverage. Furthermore, the rearward stop limitation should be effected in an easily installed, cost favorable, play free manner in the case of short master cylinders.
Federal Republic of Germany OS 31 49 628 discloses a master cylinder in which a push rod, which is provided with a spherical head, is fastened swingably via a holding member in the bore of a piston. In this connection, the holding element has a plurality of resilient projections. Some projections engage behind the push rod head while the others rest with initial stress against and therefore grab the wall of the housing bore. This force locked connection permits only a limited rearward stopping force. Therefore, the piston rod is provided with an extension which comes against a stop disk which is secured by a snap ring in the housing. This complicated construction is expensive and is time consuming to install.